Throwing the baby out with the bath water is an expression that suggests one doesn’t need to reject an entire idea, concept or practice if only part of it is good. The baby, in this sense, represents the good part. The bath water, on the other hand, is usually dirty after the baby is washed and needs to be discarded.

There are many ideas on the possible origins of this expression. Most incorrectly attribute the expression to English or Irish origin. Throwing the baby out with the bath water is first recorded in 1512, and used by the German writer, Thomas Murner, in his verse book, Die Narrenbeschworung. From Germany, the expression became commonly used in the UK, and then also became popular in France.

The idea of throwing the baby out with the bath water may be inspired by the relatively few baths taken by people in Europe even before the 16th century. Baths were often thought unhealthy, and they were difficult to prepare, since you had to draw and heat water for everyone to bathe in. This often meant that the same water might be used for a whole family’s bath, and the baby was frequently bathed last. At this point, the bath water might be quite dirty, and might obscure view of the baby. A mother wouldn’t want to mistakenly discard the baby with the dirty, murky water, not that this was likely to occur.

Since throwing the baby out with the bath water isn’t likely to occur, the expression of it, including its usage in Murner’s work, has been metaphor for the dichotomy existing in an idea or practice that is both good and bad. How can you keep the good, while still getting rid of the bad?

The expression, throwing the baby out with the bath water can be highly subjective, since individuals will define what constitutes good and bad in very different ways. A hypothetical Mr. Smith, who disapproves of human cloning might feel that other types of cloning are bad. From this viewpoint, all attempts at cloning should be rejected. Another person, who might agree with Mr. Smith that human cloning is a difficult subject could say, “Mr. Smith is throwing the baby out with the bath water. We shouldn’t clone humans, but that doesn’t mean we should reject all the practical applications of cloning plants or animals.”

Another individual might look at the scandals that have rocked the Catholic Church in recent years and decide that all aspects of Catholicism are bad, evil, or wrong. This again is throwing the baby out with the bath water. A part of something being wrong doesn’t mean the whole is wrong. Throwing the baby out with the bath water is something of a logical fallacy. The assumption is the following:

A belongs in the group A-Z
A is bad
Therefore A-Z must be bad.

A related expression might be that “one bad apple spoils the whole bunch.” In some cases it is necessary for a system to practice throwing the baby out with the bath water. In the criminal justice system, for example, an illegally obtained confession, or an illegal arrest or search can mean that any evidence resulting from these is not admissible. This is called “fruit of the poisoned tree.” Any evidence arising from a violation of the justice system is considered tainted and must be discarded.